Dissulfurirhabdus thermomarina gen. nov., sp nov., a thermophilic, autotrophic, sulfite-reducing and disproportionating deltaproteobacterium isolated from a shallow-sea hydrothermal vent

A thermophilic, anaerobic, chemolithoautotrophic bacterium, strain SH388(T), was isolated from a shallow, submarine hydrothermal vent (Kuril Islands, Russia). Cells of strain SH388(T) were Gram stain-negative short rods, 0.2-0.4 mu m in diameter and 1.0-2.5 mu m in length, and motile with flagella. The temperature range for growth was 25-58 degrees C (optimum 50 degrees C), and the pH range for growth was pH 5.0-7.0 (optimum pH 6.0-6.5). Growth of strain SH388(T) was observed in the presence of NaCl concentrations ranging from 0.5 to 4.0% (w/v) (optimum 2.0-2.5%). The strain grew chemolithoautotrophically with molecular hydrogen as electron donor, sodium sulfite as electron acceptor and bicarbonate/CO2 as a carbon source. It was also able to grow by disproportionation of sulfite and elemental sulfur but not thiosulfate. Sulfate, Fe(III) and nitrate were not used as electron acceptors either with H-2 or organic electron donors. Phylogenetic analysis based on 16S rRNA gene sequences indicated that the isolate belonged to the class Deltaproteobacteria and was most closely related to Dissulfuribacter thermophilus and Dissulfurimicrobium hydrothermale (91.6% and 90.4% sequence similarity). On the basis of its physiological properties and results of phylogenetic analyses, strain SH388(T) is considered to represent a novel species of a new genus, for which the name Dissulfurirhabdus thermomarina gen. nov., sp. nov. is proposed. The type strain of the species is SH388(T) (=DSM 100025(T)=VKM B-2960(T)). It is the first thermophilic disproportionator of sulfur compounds isolated from a shallow-sea environment.